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Discussion Starter #1
-99 c230k, 105k or so miles
-Belts were due soonish, tensioner never changed either to my knowledge

Was driving home, sounded a bit funny on idle after start, a bit deeper than usual. No warning lights and no funny business from engine or tranny so I was thinking I got a hole in the exhaust or something. Anyways in the last 1km on the way home the noise turned into a horrendous high frequency squeeking combined with some diesel engine sound and some helicopter. Yea so that's no hole in the exhaust.

Opened the hood, it appears the main serpentine belt slid on the fan pulley and belt tensioner pulley, slighty backwards towards the engine. Belt was hitting the engine block and essentially shaving bits of the belt off. Now below in the picture you will see one of the fan pulley's bolts to be loose and also a visible gap related to the bolt being loose.



Theories?

So going to need a new serpentine belt. But uh the belt itself didn't cause this I don't think... unless it was old and loose which led to the sliding and then the friction of hitting the block causing the bolt to come loose?

Fan pulley's bolt wasn't tightened properly last time it was off maybe? (About 3k miles) leading to the slow progression of this?

Tensioner? How to test if tensioner is bad?

I'm pretty clueless in this area, always been on a need to know basis as stuff came up.

Any input appreciated.
 

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2010 E350, 2005 Tundra Sold the 1998 C230
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322 Posts
Pop the old belt off and tighten everything down. You can check the tension on the tensioner at this point, should be able to tell if it is still good or not. Looks like something loosened up, just lucky the belt didn't come completely off. Put a new belt on and run it a while and see what happens.
 

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2000 C230 Kompressor Special Edition
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1,173 Posts
Be sure to use loctite on your bolts. Blue would work for those bolts. There are to many vibrations and the bolts are old.
 

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2000 C230 Kompressor
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141 Posts
Something similar happened to me, I believe blue loctite should be fine, but I used lock washers on them, and haven't had the issue come back in a year. However, I ended up replacing the water pump for the peace of mind that the bearing might have been damaged from the wobbling.
 

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Discussion Starter #5
Going to attempt to fix things up today, if it doesn't go smoothly then I don't really got the time for it and I'll take it to a shop. So I'll try to take some pics of the stuff I do get through for future reference for others.
 

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99 C280
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233 Posts
I would guess the tensioner is failing. If funds are not an issue, I would replace the belt, tensioner, idler, and water pump.
 

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Discussion Starter #7
Tensioner seemed fine. Primary issue was the bolts coming loose I believe. I don't think it caused further damage since the pulley was just slightly out of line and not at a wobbling state. I do agree it would be wise to change out some other stuff for peace of mind but in this case I'm inclined to think I got away with one as everything sounds normal with those bolts back in place.
 
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